Process of making absorbent materials and compounds mande therefrom



Patented Aug 22, 1933 UN l TED STATES PATENT- OFFICE,

PROCESS OF MAKING ABSORBENT TERIALS AND COMPOUNDS MADE THERE- FROM poration of Delaware No Drawing. Application April 3, 1930 Serial No. 441,418

27 Claims.

Our invention relates to a process of treating absorptive material for use in explosive compositions and to explosives made with su: h absorptive material incorporated therein.

Explosive compositions such as the so-called straight dynamites, ammonia dynamites, gelatin dynamites, permissible explosives, etc., typically comprise a liquid explosive component or sensitizer, such as nitroglycerin, nitroglycol or nitropolyglycerin, an explosive salt, such as ammonium nitrate, and/or an oxygen carrier such as sodium nitrate, and an absorbent or absorbents which are generally called fillers. These fillers usually comprise carbonaceous combustible material. Vegetable materials, such as plant tissues, are particularly suited as absorbent material for explosive compositions. Wood pulp, sawdust, bagasse pith, balsa wood, ground cork, and corn meal are among the fillers commonly used before the present invention.

In certain types of relatively high density explosives, for example the so-called straight dynamites which comprise a relatively high liquid explosive compound, absorbents or fillers of great absorptive power are required so that no exudation, that is, voluntary separation of the liquid component from the solid component, occurs, since exudation gives rise to a dangerous condition.

It is well known that for certain operations, for example, in the mining of coal, it is desirable and advantageous to extend the distribution of the explosive charge in the bore hole as much as possible without increasing the weight or power of the explosive charge. In such cases, explosives of low density, i. e., high cartridge count per unit weight, are required. In order to obtain explosives of low density, fillers of extremely low density are commonly used, for example bagasse pith, balsa wood, sphagnum moss, etc. Extremely low density fillers are characterized by great absorptive power for the liquid explosive component of the explosive composition. The proportion of low density absorbent which may be used in an explosive composition is limited, as explosive compositions containing large proportions of such fillers do not possess the necessary sensitiveness to propagation, by which is meant, that when cartridges are placed at a predetermined distance apart the explosion of one cartridge does not propagate to another cartridge placed at a sufflciently long distance. It is well known to those skilled in the art that the sensitiveness of explosive compositions is mainly due to the presence therein of nitroglycerin or other liquid component and that the sensitiveness to a great extent is obtained through the unabsorbed liquid component held as surface liquid on the particles of the solid component. In low density explosive compositions comprising relatively small proportions of nitroglycerin or other liquid explosive -component and relatively high proportions of low density absorbents, the small amount of liquid component is completely or nearly completely absorbed in the low density filler.

This inevitably results in low sensitiveness which is undesirable as low sensitiveness of an explosive composition results in incomplete detonation of the charge in the bore hole and, aside from inefficiency, undetonated cartridges are often the cause of serious accidents or loss of life. The desirability of having carbonaceous materials or fillers available which would be of low density and at. the same time of low absorbent power.will therefore be apparent.

An object of the present invention is the process of treating absorptive material to decrease its absorptive properties.

A further object of our invention is to lower the density of absorbent material and increase the value thereof as an ingredient of explosive compositions.

Another object of our invention is the production of an explosive composition having low density.

A still further object of our invention is to improve generally on absorbent materials and explosives containing such ingredients.

Other objects will appear as the description proceeds.

These objects are accomplished by the following invention in which we have now found that the carbonaceous absorbent materials as used for explosive compositions can be so modified as to decrease their absorbent capacity without impairing their low density, and our invention comprises the methods of modifying the absorbent materials, the'novel materials resulting therefrom, as well as the low density explosives obtained by incorporating therein our improved absorbents.

Our method of treating or modifying the absorbent plant tissues consists in bringing them into intimate contact with organic materials of a more or less colloidal nature or, apparent high molecular weight; when this is done through a liquid medium, that is to say, in suspension, dispersion, emulsion or solution, the plant tissue will absorb or otherwise associate with the foreign material and thereby lose a substantial part of its absorbent power without losing its low density or its value as a carbaceous combustible material.

We are aware that it has been suggested to fill the pores or cells of plant tissues with inorganic salts which take part in the explosives reaction, particularly with sodium and ammonium nitrates; this practice, however, is a rather dangerous operation as it involves heating of finely comminuted organic materials with nitrated salts, and special precautions have to be taken to avoid explosions or dangerous confiagrations. For this reason it has also been suggested to use in connection with the above nitrated salts, some salts containing large amounts of water of crystallization. This water remains in the finished explosive composition as inert material and consequently depreciates the explosive strength.

Certain of the low density plant tissues, for example, bagasse pith, sphagnum moss, etc., are easily broken down to a fine powder or dust by screening, agitation during drying, and other handling normal to plant operation. Thetreating of these plant tissues with organic amorphous substances tends in general to stiffen the tissue and render it less brittle. In this respect, our novel fillers distinguish themselves favorably from the untreated plant tissue. Plant tissues which have been impregnated with inorganic salts, for example, sodium and ammonium nitrates, etc., are especially brittle and on normal handling the tissue tends to break down to a fine powder or dust and in breaking down there is a partial separation of the plant tissue and the impregnated inorganic salt or salts. Treatment with organic, amorphous substances according to our invention tends to stifien and toughen the fibers of plant tissues which have been impregnated with inorganic salts, and tends to prevent the breaking of the fibers and the separation of the inorganic salts from the plant tissue.

The carbonaceous, organic materials which we have found useful for the treatment or impreg-, nation of the absorbent plant tissues are of vegetable, mineral, animal, or synthetic nature: the following have been found to give excellent re- .sults: carbohydrates, such as starchy materials,

refined starch glucose, etc.; modified cellulose, such as viscose; albuminoids and proteins; gelatinous substances of animal and vegetable origin, such as gelatin, isinglass, Irish moss, agar-agar, etc. casein and its derivatives; waxes and paraflins; natural and synthetic resins, shellac, rubber, asphaltum, and others. It will be observed that the above substances appear usually in the amorphous form as distinguished from crystalline substances. It will be understood that we do not contemplate impregnating plant tissues with organic explosive compounds, whether they be soluble or insoluble in nitroglycerin or other liquid nitrocompounds, such explosive compounds being nitrocellulose, nitrostarches, organic peroxides, etc. It will be seen from the above that the impregnating materials which we use i 0 noval treatment of plant tissues are organic, amorphous substances of non-explosive properties, that is to say, which are inert or stable toward impact of an explosive wave. The use of organic materials which are substantially soluble in nitroglycerin would defeat the purpose of using our novel fillers in low density type explosives, as the nitroglycerin would penetrate through the coating into the interior of the absorbent material and when used in such explosive compositions would gradually render these insensitive.

The methods of treating the plant tissues with our impregnating substances will vary somewhat with the nature of the plant tissue and the impregnating material. We generally prefer to mix the impregnating material with or dissolve it in a liquid medium and stir the plant tissue with this liquid preparation into a homogeneous mass. A more intimate contact and better impregnation of the minute pores and cells of the plant tissues can be obtained by boiling said mass or applying vacuum or even elevated pressure thereto. The plant tissue absorbs practically all of the liquid used and is then dried in any convenient manner.

As an illustrative example of one method of treatment according to our invention, we take a plant tissue such as bagasse pith, balsa wood flour, etc., and treat it in the following manner: starch is first stirred with a small amount of cold water to form a homogeneous suspension. This suspension is then poured into a large volume of boiling water and boiled for a short time in order to burst the starch cells, producing the familiar starch paste. The volume of water used in preparing the starch paste may be as low as ten parts of water to one part of starch or as high as fifty parts of water to one part of starch. In preparing our starch paste, we prefer to use about fifteen to twenty parts of water to one part of starch as we have found that smaller volumes of water form such thick viscous solutions that it is difficult to thoroughly incorporate the starch paste with the plant tissue and the starch does not properly penetrate the cellular structure of the plant tissue.

These starch pastes prepared as described above may be added to the plant tissue in a number of ways. The starch solution may be added while boiling hot or while cold or at any intermediate temperature. We have found that the temperature of the starch paste when added is immaterial as long as viscosity of the paste is such that it will substantially penetrate and fill the cellular structure of the plant tissue. It is of course immaterial if the plant tissue is added to the starch paste or vice versa. The quantity of the starch paste used in treating the plant tissue may also be varied. It may be as low as one part of starch paste to two parts of plant tissue or as high as 12 parts of starch paste to one part of plant tissue. It is advisable to thoroughly mix the plant tissue with the liquid paste and this is best performed in mechanical mixing apparatus. After thoroughly mixing the starch paste with the plant tissue, the mixture is passed through a screen to break any agglomerates formed, dried in any convenient manner and ground if desired. By variations in the concentration of the starch paste and in the amount of the starch paste used in treating the plant tissue, we may vary the proportion of starch in the dry treated plant tissue. We prefer to so vary the proportions that the treated product will contain from three to thirty parts of starch per hundred parts of plant tissue. By treating plant tissue in the manner described above, plant tissue is obtained which has foreign starch deposited within its pores or cells and the density of the treated material is lower and it has a reduced absorption power for nitroglycerin.

Another method of impregnating plant tissue with starch consists in preparing a suspension of the material in boiling water and slowly adding wetted starch thereto. The formation of the starch paste and impregnation occur practically simultaneously; the treated plant tissue is then dried and a filler for explosives of properties similar to those of the above material is obtained.

The starches which we have found most advantageous in our method of impregnation are those derived from corn or potatoes, but other starches will function with similar efliciency. Soluble so-called cold-water starch and similar preparations obtained by chemical treatment, or heat treatment of ordinary starches and which are capable of being made into a viscous mix-- ture or solution in cold water, will produce by impregnation, fillers of similar reduced density and absorptive power.

Treatment of plant tissues with vegetable or animal gelatin is eflected in a manner similar to that described for treating with starch by preparing a viscous aqueous solution of the gelatin, steeping the plant tissue therein, and drying the treated material. -The gelatin appears to be deposited within the pores and voids andforms a kind of film over the plant tissue particles. The gelatin treated fillers show a lower density and absorption value than the untreated material.

Impregnation of a plant tissue with a cellulosic material can be effected as follows: We dissolve parts cellulose xanthate in, for instance, 1500 parts of water; stir 160 parts of bagasse pith or sphagnum moss into the above solution until it is practically completely absorbed by the plant tissue. We then place the saturated material in a suitable dipping device and dip the whole in a dilute nitric acid, containing at least sufilcient acid to neutralize the free alkali present and to also regenerate the cellulose. We then press out the excess acid on a filter and dip the treated plant tissue in a weak solution of ammonia, whereby any excess acid is neutralized. The excess liquid is then filtered off or squeezed out, the treated pith or moss washed with water and dried. In this way we produce an absorbent compound of bagasse pith or sphagnum moss which is impregnated or intimately associated with hydrocellulose. This treated plant tissue is neutral to litmus, low in density and lower in absorption capacity for nitroglycerin and similar liquid explosive compounds than the original plant tissue.

In treating plant tissues with paraflin, resins, shellac, rubber, asphaltum, etc., which materials are substantially insoluble in or difficultly miscible with water, we preferably use an organic solvent to dissolve the impregnating material such as methanol for shellac, benzene for rubber, etc. The treatment consists then in allowing the plant tissue to absorb completely the solution and drying for elimination of the solvent. The amorphous organic material is in this manner deposited within the pores, cells, or voids of the plant tissue, and decreases its absorption capacity for nitroglycerin.

It has been suggested to impregnate plant tissue with inert salts, explosives salts, oxidizing salts or combinations thereof such as sodium chloride, ammonium perchlorate, ammonium nitrate and/or sodium nitrate. Impregnation of plant tissues with such inorganic salts produces a material of substantially lower density than mixtures of. the salt or salts with the plant tissue. Also the absorptive power of the plant tissue for nitroglycerin is substantially reduced by such impregnation. We have found that when plant tissue which has been impregnated with inorganic salt or salts is treated in acordance with our invention as described above, the absorptive power for nitroglycerin is further substantially reduced and there is a. further decrease in the density. We may, therefore, treat as described above, plant tissue which has. previously been impregnated with inorganic salts. We prefer, however, when carrying out the treatment with starch or other organic material to accomplish both the impregnation with the inorganic salt or salts and the treatment with'the organic amorphous material in the same operation. This may be accomplished by dissolving the salt or salts (e. g. nitrate or nitrates) and the organic amorphous material in the same solution before adding the solution to the plant tissue. When treating with organic amorphous materials, for example, paraffin, resins, shellac, etc. which require a solvent other than water, the impregnation with the inorganio'salt or salts and the treatment will, obviously, have to be carried out in separate operations. 'It is to be understood that the inorganic compound and organic materialmay be applied in liquid medium either separately or together.

ICE)

The amount of amorphous, non-explosive, or-

ganic material deposited upon the plant tissue can be varied, and in this manner fillers for explosives produced which will have a wide range of density and absorption capacity. The above described methods of impregnation can also be varied to suit the particular properties of the fillers and impregnating materials, and any method of treatment may be used which will cause the impregnating material to be deposited within the pores, voids, or cellular structure of the plant tissue or form a film-like structure covering the particle thereof.

It will be understood that our invention is not limited to the use of a single impregnating material, but that several different amorphous, non-' explosive, organic materials can be caused to be absorbed simultaneously by the plant tissue or that one or more of the impregnating materials can be applied in successive treatments, if desired. Also, it will be understood that we may treat any one of the many absorbents commonly used in explosive compositions or any combination of the absorbents.

Our novel treated fillers are distinguished by reduced capacity for absorbing nitroglycerin, nitroglycol, nitropolyglycerin and other liquid explosive components as compared with the untreated material. The rate of decrease will depend upon the amount or kind of impregnating material deposited upon the particular filler. The impregnation of the plant tissues by our novel method introduced additional carbonaceous matter but as the density of the treated filler is usually lower or unchanged, 'only slight adjustments as to oxygen balance of the explosive compositions will be required. Adjustments or calculations as to this are routine matters with those skilled in this art and need not be described in detail.

The following gives in table form the absorptive power of various fillers before and after treatmentraccording to our invention.

100 parts Abosrpo1 filler tion cawill abpacity sorb in 01' parts that of nitrountreated glycerin fillet Sphagnum moss, untreated 448 100 Sphagnum moss treated, containing about 16% star 293 65 Sphagnum moss treated, containing about 24% starch 155 34. 6 Sphagnum moss treated, containing about 24% gelatin 240 54 Sphagnum moss treated, containing about 6% starch and 3% gelatin 272 61 Sphagnum moss treated, containing about 5.7% starch, 2.7% gelatin, and 1.1% glucose 266 59 Sphagnum moss treated, containing about 24% Irish moss .s 169 37. 7 Sphagnum moss treated agar-agar 174 39 Balsa wood, untreatc 378 100 Balsa wood treated,

Irish moss 170 45 Balsa wood treated, containing about 24% agar-agar 153 40. 5 Balsa wood treated, containing about 24% starch 186 49 Ground cork, untreated. 100 100 Ground cork treated, containing about 24% agar-agar 64 33. 7 Ground cork treated, containing about 24% Irish moss 85 45 Ground cork treated, containing about 24% starch 60 31. 6 Wood pulp, untreated 280 100 Same wood pulp treated, containing about 24% starch 63 22. 5 Same wood pulp treated, containing about 24% Irish moss 250 89 Bagasse pith 21 parts impregnated with ammonium nitrate 79 parts 82 100 llagasse pith 21 parts impregnated with ammonium nitrate 75 parts and starch 4 parts 61 74 Bagasse pith 10 parts impregnated with ammonium nitrate 69 parts and sodium nitrate 12 parts. 72. 5 100 Bagasse pith 8 parts impregnated with ammonium nitrate 07 parts and sodium nitrate 11 parts treated with starch 4 parts 45 62. 1 Wood pulp 14 parts impregnated with arnmonium nitrate 42 parts, and sodium nitrate 44 parts 33 100 Wood pulp 13.5 parts impregnated with ammonium nitrate 41 parts, sodium nitrate 42 parts, and treated with starch 3.5 parts... 22 07.0

Nitroglycerin 12 Nitroglyc 3 Ammonium nitrate 56 Sodium nitrate; 10 Bagasse pith treated with 15% starch 18 Chalk 1 The properties of this explosive composition are as follows:-

Sensitiveness to propagation 10" Rate of detonation 2270 m/sec. No. of 1 Ax8 ctgs. per 50 lbs 235 With untreated bagasse pith, an explosive composition of the above type and satisfactory sensitiveness will have a cartridge count of around 220.

A typical example of explosive composition compounded with sphagnum moss which has been treated with starch according to the method described is as follows:

Nitroglycerin 7.5 Dinitroethyleneglycol 2.5 Ammonium nitrate 57.5 Sodium nitrate 15.0 Chalk 0.5

Sphagnum moss treated with 23 starch 17.0

The ballistic properties of this explosive are as follows:

Sensitiveness to propagation 10" Rate of detonation 1720 m/sec. Number of 1%x8" ctgs./50 lbs. 254

Nitroglycerin 12 Nitroglycol 3 Filler comprising bagasse pith impregnated with 65% ammonium nitrate, 10% sodium nitrate and treated with 5% starch 84 Chalk 1 The properties of this explosive composition are as follows:

Sensitiveness to propagation 10" Rate of detonation 2000 m/sec. No. of 1%x8 ctgs. per 50 lbs 275 With a filler of the above composition which has not been impregnated with starch, an explosive composition of the above type and satisfactory sensitive'ness will have a cartridge count of around 230. I

A great variety of explosive compositions of satisfactory Sensitiveness to propagation and ballistic properties can be compounded with our novel treated fillers which would be impossible with fillers not so treated. It will be understood that we do not limit ourselves to the compositions given above as they are merely examples of compositions compounded with our novel treated fillers.

We claim:

1. The process for producing a. combustible ingredient for use in high explosive compositions, which comprises impregnating a carbonaceous absorbent material with a non-explosive, amorphous, organic material, substantially insoluble in nitroglycerin.

2. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating a. plant tissue with a non-explosive, amorphous, organic material, substantially insoluble in nitroglycerin.

3. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating a carbonaceous absorbent material with a. carbohydrate, which is amorphous and substantially insoluble in nitroglycerin.

4. The process for producing a. combustible ingredient for use in high explosive compositions, which comprises impregnating a carbonaceous absorbent material with starch.

5. A process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating wood pulp with a non-explosive, amorphous, organic material, substantially insoluble in nitroglycerin.

6. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating wood pulp with starch.

'7. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating bagasse pith with a non-explosive, amorphous, organic material, substantially insoluble in nitroglycerin.

8. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating bagasse pith with starch.

9. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating an absorbent moss with a non-explosive, amorphous, organic material, substantially insoluble in nitroglycerin.

10. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating an absorbent moss with starch.

11. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating sphagnum moss with starch.

12. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating a carbonaceous absorbent material with a non-explosive, amorphous, organic material, substantially insoluble in nitroglycerin, said material being applied in a liquid medium, the liquid medium being subsequently removed.

13. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating a carbonaceous absorbent material with starch in an. aqueous medium, the water being subsequently removed.

14. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating a carbonaceous absorbent material with at least one inorganic nitrate and-a non-explosive, amorphous, organic material, substantially insoluble in nitroglycerin.

15. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating a carbonaceous absorbent material with at least one inorganic nitrate and a carbohydrate, which is amorphous and substantially insoluble in nitroglycerin.

16. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating a carbonaceous absorbent material with at least one inorganic nitrate and starch.

17. The process for producing a combustible ingredient for use in high explosive compositions,

which comprises impregnating a carbonaceous 19. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating a carbonaceous absorbent material with ammonium nitrate and starch.

20. The process for producing a combustible ingredient for use in high explosive compositions, which comprises impregnating a carbonaceous absorbent with ammonium nitrate and starch in aqueous medium, the water being subsequently removed.

21. An explosive composition comprising a liquid nitric ester and a carbonaceous absorbent material, said carbonaceous material comprising a plant tissue impregnated with a non-explosive, amorphous, organic material, substantially insoluble in nitroglycerin.

22. An explosive composition comprising a liquid nitric ester and a carbonaceous absorbent material, said carbonaceous material comprising a plant tissue impregnated with a carbohydrate, which is amorphous and substantially insoluble in nitroglycerin.

23. An explosive composition comprising a liquid nitric ester and a carbonaceous absorbent material, said carbonaceous material comprising a plant tissue impregnated with starch.

24. An explosive composition comprising a liquid nitric ester and a carbonaceous absorbent material, said carbonaceous material comprising a plant tissue impregnated with at least one inorganic nitrate and a non-explosive, amorphous, organic material, substantially insoluble in nitroglycerin.

v 1 25. An explosive composition comprising a iiquid nitric ester and a carbonaceous absorbent material, said carbonaceous material comprising a plant tissue impregnated with at least one inorganic nitrate and starch.

- 1 26. An explosive composition comprising nitro- 

